Cannot Parse a Custom Node as a Function Input to Another Custom Node In The Material Editor

Cannot parse a Custom node as a function input to another Custom node in material editor. This is working as expected in 4.18 CL# 3832480.

Found in 4.19 CL# 4033788, 4.20 CL# 4302132, and 4.21 CL# 4329255

This is a regression.

1. Go to: UE_4.20\Engine\ConfigConsoleVariables.ini and uncomment r.ShaderDevelopmentMode=1
2. Open the attached project
3. Open the material in the project Preview the second custom node

Results:
An error will pop up like the attached image and take focus

Expected:
The material would compile without error